The invention relates to a process for the production of a sinterable finely divided molding compound by homopolymerization of vinyl chloride in aqueous suspension, in which, besides a suspending agent, a cosuspending agent from the class of sulfated carbohydrate esters is used, and its use for the production of separator plates for electric cells.
It is known to use molding compounds with a base of polyvinyl chloride for the production of sintered molded articles, for example, of separator plates for electric cells.
A process is described in DE-C No. 3-23 10 431 in which, for the production of the suspension polymer, a free emulsifier acid is used, besides the usual suspension stabilizers and nonionic wetting agents. From these polymers, sintered plates with good wettability and good mechanical properties can indeed be produced, but their electrical resistance is comparatively high.
In DE-A No. 33 34 667 a process is described, in which after vinyl chloride polymerization, before drying of the finely divided polymer, at least one nonionic wetting agent and one nonsurfactant acid are added. Even with polymers of this type, it is not possible to produce sintered plates, which, along with good mechanical properties have a slight electrical resistance.
In the course of optimizing the performance characteristics of electric cells, especially of batteries for use in motor vehicles, it was found that the cold starting performance of a battery can be considerably improved by a reduced electrical resistance of the sintered plates employed therein. It is thus desirable to produce sintered plates, which exhibit as small electrical resistance at possible. Sintered plates are also desired, which, with given plate thickness and strength, exhibit a high porosity. A high porosity of the sintered plate allows higher acid storage volumes and makes a reduction of the battery volume possible.